Recombination systems for electric accumulator or storage batteries have been pair of prior art for over 25 years. A system of that type is described in the DE-PS (German patent) 20088218. A corresponding catalyst is described in DE-PS 2213219, absorbers in DE 2237950 C3 and DE 2265701 C3.
To date, their basic design concept has remained essentially unchanged. The core feature of these recombiners is a catalyst-coated rod for instance of copper, alumina or the like. The catalysts most commonly used are platinum metals and especially palladium. The catalytic rod is centrally mounted in a tube of a porous material, for instance a gas-permeable ceramic tube; the remaining space in the tube is filled with absorption material. Absorbers employed include lead oxide, silver nitrate, iron oxide, cupric oxide and the like. The tube is enclosed in free-standing fashion in a gas-tight container preferably consisting of a synthetic material, and its ends are sealed. The container is provided with an adapter union by way of which it is connected to a storage battery for gas intake and water removal.
The hydrogen and oxygen gases which constitute an oxyhydrogen gas mixture and form during the operation of a battery are channeled into the container via the adapter union, pass by the porous tube and the absorbers and on contact with the catalyst are recombined into water. The reaction is exothennal so that the water precipitates in the form of water vapor on the container wall where it is condensed, and then flows back into the battery via the adapter.
In the publications mentioned, the container is in the form of a single unit directly incorporating the adapter, for example an injection-molded structure with an opening accepting, in gas-tight fashion, the catalytic unit described above. The oxyhydrogen gas cannot escape.
Prior art also includes configurations in which the connecting adapter and the container are produced separately and are assembled, by means of a retaining element, after the catalytic unit has been installed, whereupon they are locked together for instance by welding.
These earlier recombination systems have a number of drawbacks. While the individual elements, if plastic, are easy to make, their installation is complex and not automatable. In view of the exothermal reaction the entire, complex retaining element must consist of a high-quality, heat-resistant synthetic material. Separating the materials, as required nowadays, for disposal or even recycling of the individual components is possible at considerable cost only. In terms of its utilization, the size of the container is limited and the dimensions of the catalytic unit are tailored to a gas volume that is to be expected under normal operating conditions. However, in the event the gas volume is larger due to an overload, a higher charging current or the like, the container will fill up with water vapor, producing an internal pressure that prevents the intake of additional gas. Proper function of the unit is no longer assured. Yet any uncontrolled escape of oxyhydrogen gas must be avoided. It has also been found that any overload will substantially reduce the effectiveness of the catalytic unit since the oxyhydrogen gas entering the container no longer reaches the surface of the catalyst in reliable and controllable fashion.
Simply exhausting oxyhydrogen gas to the outside would pose an ignition hazard whereby the flame might propagate all the way into the battery.
Apart from the cost-related drawbacks in terms of production, assembly and disposal or recycling, the prime concern is inadequate safety in the event of an overload. Recombination systems are predominantly employed in conjunction with stand-by storage batteries, emergency-power units and the like and should ensure dependable operation, with a minimum of maintenance even over extended periods of time.